Piston



A. L. NELSON Feb. 12, 1935.

PISTON 2 Sheets-Sheet 1 Original Filed May 15, 1929 A. NELSON Feb. 12, 1935.

PISTON Original Filod May 15, 1929 2 Sheets-Sheet 2 Qvwentoz W 2" I $259 at wy w.

Patented Feb. 12, 1935 PISTON Adolph L. Nelson, Detroit, Mich.

Application May 15, 1929, Serial No. 363,127 Renewed December 29, 1930 15 Claims.

This invention relates to pistons, particularly to pistons for use in automobile and other internal combustion engines.

The invention is adapted particularly to a piston formed of light Weight material with cylinderbearing portions spaced by struts of relatively inexpansible material, the cylinder-bearing portions being connected to the head by lateral ties. In pistons of this description the skirt normally has a greater diametrical thermal expansion in the circumferential zone of the ties than at other points on the skirt, and the present invention meets this situation by forming said circumferential zone on a smaller diameter than the normal diameter of the skirt.

Other objects and advantages of the invention will become apparent as the description proceeds.-

While preferred forms of the invention have been disclosed for purposes of illustration, it should be understood that various changes may be made in the structure without departing from. the spirit and scope of the invention as hereinafter set forth and claimed.

In the drawings:

Fig. 1 is a side elevation of the invention.

Fig. 2 is a side elevation partly in section taken at right angles to Fig. 1.

Fig. 3 is a bottom plan view of the piston.

Fig. 4 is a section taken on line 4-4 of Fig. 1.

Fig. 5 is a side elevation of a modified form of the invention.

Fig. 6 is a side elevation of an additional species.

Fig. '7 is a cross section of a further possible modification.

Referring to the drawings more specifically, the piston comprises a head 10, piers 11 depending from the head, and piston pin bosses 12 formed in the piers. The skirt includes opposite cylinder-bearing portions 13, which, in the specific examples illustrated, are connected to each other at their lower ends by arc-shaped portions 14, but this latter feature may be omitted. When the arc-shaped portions 14 are used they are preferably relieved or cut back as clearly indicated in Fi s. 1 and 2.

The parts thus far described are preferably formed of some light material such as an aluminum alloy. The struts 15, which are of a material, such as steel, having a lower coefiicient of expansion that the material of the piston head and bearing portions 13, extend across the piers between the bearing portions. Ties 16 extend laterally from the piers and form homogeneous cona piston embodying piston showing a nections between the piers and the bearing portions.

In the piston illustrated in Figs. 1 to4 these ties 16 extend from each lateral side of the pin boss on both the inside and outside of the struts, but this arrangement of the ties can be varied, as the ties may be omitted on either the inside or the outside of the struts. or they may be used only on diagonally opposite sides of the piston, as shown in Fig. 7.

In pistons of this type with the homogeneous ties extending laterally from the piers to the bearing portions, the presence of the ties causes the bearing portions to have a slightly greater thermal expansion in the circumferential zone adjacent the ties than at other points. In the species of Figs. 1 to 4 this extra expansion is taken care of by dividing each cylinder-bearing portion into three belts by cutting grooves 17 circumferentially across the bearing portion. The middle belt 18 is then ground down so that when cold it lies below the surfaces of the upper belt 19 and the lower belt 20. However, the amount by which the diameter of this middle belt is reduced is just enough to compensate for the extra expansion due to the ties, and when the skirt is at operating temperature the middle belt is closely of the same diameter as the upper and lower belts; y

In Fig. 5 a similar result is obtained by cutting a circumferential groove 21 in the zone of the lateral ties. The upper end of the skirt is then ground on a taper with the wide end of the taper at the top of the skirt and the narrow end of thetaper at groove 21. The lower end of the skirt is ground on a taper with the wide end of the taper at the bottom of the skirt and the narrow end of the taper at groove 21. Thus the skirt tapers inwardly toward the groove 21 from both top and bottom of the skirt, resulting in a skirt that has a smaller diameter, when cold, in the circumferential zone of the homogeneous ties than at the top and bottom ends of the skirt. Under an increase in temperature the part of the skirt in the zone of the ties expands faster diametrically of the piston than the top and botthe skirt. Here a rise in temperature causes the upper end of the skirt to expand faster than the lower end, causing the skirt to assume a shape with the bearing faces parallel to the vertical lines of the cylinder.

In all of the forms disclosed the parts of the bearing portions lying in the circumferential zone of the ties is formed on a diameter smaller than the normal diameter of the skirt. The term normal diameter of the skirt as used herein means the diameter of the skirt at the part where it has its closest clearance in the bore when cold.

The present invention also contemplates the use of slots in the skirt in combination with lateral ties from the piers to the cylinder-bearing pertions. For instance, a slot 22 as illustrated in Fig. 2 may extend from top to bottom of one or both of the cylinder-bearing portions. This type of slotting may be used with any location of the ties, but is particularly adapted to the arrangement where the ties join the middle of the bearing portions as inFig. 2.

Another type of slotting is shown in Fig. 5, where one of the bearing portions is formed with a slot 23 extending partway downwardly, while slot 24 runs partway upwardly into the other bearing portion.

A still further arrangement of slots is illustrated in Fig. 6, where one or both of the bearing portions may be formed with a slot 25 running partway downwardly from the upper edge there- 0 I claim:

1. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a

skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, ties extending laterally from the piers to the bearing portions, the ties being homogeneous with the piers and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diameter of the skirt.

2. A piston comprising a head formed of light weightmaterial, piers depending from the head and having piston pin bearings formed therein,.

a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending laterally from a pier to a bearing portion, the tie being homogeneous with the pier and the bearing portion, the parts of the bearing portion lying in the circumferential zone of the tie being formed with a diameter smaller than the normal diameter of the skirt.

3. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, strutsof relatively inexpansible material extending between the cylinder-bearing portions, ties extending laterally from a pier to a oylinderbearing portion, the ties being homogeneous with the piers-and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diameter of the skirt.

4. A piston comprising a head fomed of light weight material, piers depending from the head and having'pistcn pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, 9. tie extending from each lateral side of each pier to the bearing portions, the ties being homogeneous with the piers and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diameter skirt.

5. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions. struts of relatively inexpansible material extending between the cylinder-bearing portions, a pair of ties extending from each lateral side of each pier to the bearing portions, the ties being homogeneous with the piers and bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diameter of the skirt.

6. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending from each lateral side of each piston pin boss to the bearing portions, the ties joining the bearing portions substantially midway of the vertical length of the bearing portions, the ties being homogeneous with the piers and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diameter of the skirt.

7. A piston comprising a head formed of light weight material, piers depending from the head and having'piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending from each lateral side of each piston pin boss to the bearing portions, the ties joining the bearing portions substantially midway of the vertical length of the bearing portions, the ties being homogeneous with the piers and the bearing portions, the skirt being cut by two circumferential grooves that divide the skirt into three circumferential zones, the middle zone being formed with a diameter smaller than the other zones.

8. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending from each lateral side of each pier to the bearing portions, the ties being located above the axis of the piston pin bearings and joining the bearing portions near the ends of the bearing portions next to the head, the ties being homogeneous with the piers and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with a diameter smaller than the normal diof the pier to the bearing portions, the ties being located above the axis of the piston pin bearings and joining the bearing portions near the ends of the bearing portions next to the head, the ties being homogeneous with the piers and the bearing portions, the skirt being formed on a taper with the narrow end of the taper adjacent the head of the piston and the wide end of the taper at the bottom of the skirt.

10. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, ties extending laterally from the piers to the bearing portions, the ties being homogeneous with the piers and the bearing portions, the parts of the bearing portions lying in the circumferential zone of the ties being formed with an outside diameter smaller than the largest outside diameter of the cylinder-bearing portions when the piston is cold.

11. A piston comprising a. head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending from each lateral side of each piston pin boss to the bearing portions, the ties joining the bearing portions substantially midway of the vertical length of the bearing portions, the ties being homogeneous with the piers and the bearing portions, the outer effective bearing surfaces of the upper end of the skirt being formed with a first taper, the wide end of the first taper being adjacent the head of the piston, and the narrow end of the first taper being adjacent the circumferential zone of the ties, the outer effective bearing surfaces of the lower end of the skirt being formed with a second taper, the wide end of the second taper being adjacent the lower open end of the skirt and the narrow end of the second taper being adjacent the circumferential zone of the ties.

12. A piston comprising a head formed of light-weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing p01- tions, struts of relatively inexpansible material extending between the cylinder-bearing portions, the struts being in the form of flat plates apertured for passage of the piston pin, ties extending laterally along the inner arid outer side of each strut from each pier to each cylinder-bearing portion, each tie being in contact with a strut throughout the length of the tie, the ties being homogeneous with the piers and the bearing portions, the circumferential belt of each cylinderbearing portion which lies in the circumferential zone of the ties being formed with an outside diameter smaller than the largest effective outside diameter of the cylinder-bearing portions.

13. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending outwardly from each lateral side of each piston pin boss to the bearing portions, the ties being homogeneous with the piers and the bearing portions, the outer efiective bearing surfaces of the skirt being so formed that when the skirt is cold the upper and lower ends of the cylinderbearing portions have diameters larger than the diameter of an intermediate circumferential zone of the cylinder-bearing portions, the diameters increasing gradually from said intermediate zone toward each end of the cylinder-bearing portions. 14. A piston comprising a head formed of light weight material, piers depending from the head and having piston pin bearings formed therein, a skirt comprising cylinder-bearing portions, struts of relatively inexpansible material extending between the cylinder-bearing portions, a tie extending outwardly from each lateral side of each piston pin boss to the bearing portions, the

ties being homogeneous with the piers and the bearing portions, the outer effective bearing surfaces of the skirt being so formed that when the skirt is cold the diameter of the skirt at the zone of the cylinder-bearing portions joined by the ties is the smallest skirt diameter, the skirt diameter increasing gradually from said smallest diameter toward each end of the skirt.

15. A piston comprising a head and a skirt, the skirt being so formed that when the skirt is cold the diameter of anintermediate circumferential zone of the skirt is the smallest skirt diameter, the skirt diameter increasing gradually from said smallest diameter toward each end of the skirt.

ADOLPH L. NELSON. 

